1. Field of the Invention
The present invention generally concerns amplifier design and amplifier operation, particularly for wireless cellular radio communications applications where occasional jamming is prevalent.
The present invention particularly concerns the realization by both design and operation of a Low Noise Amplifiers (LNA) simultaneously improved in (i) dynamic range and (ii) overall power consumption, these seemingly contradictory requirements being satisfied by optimizing power consumption in the LNA in consideration of its instant operating environment.
The present invention further particularly concerns an ungrounded power detector that is both fast and sensitive to detect the output power of, for example, a LNA.
2. Description of the Prior Art
2.1 Low Noise Amplifiers, and Amplifier Operation in the Presence of Jamming
With the explosive growth of wireless communications, the airwaves are rapidly being filled with signals of varying strengths and frequencies. Immunity to jamming has subsequently become a significant concern to any communication system. This is especially true for a mobile communication system, such as a cellular phone, as it is difficult to predict the jamming environment the system will be exposed to. At the same time, the need for portability, and thus long battery life, requires the system to consume as little power as possible.
In a typical wireless system, filtering before the low-noise amplifier can reject most jammers. However, a high rejection ratio incurs high insertion loss—a direct contributor of receiver sensitivity degradation. In addition, many close-in jammers are impossible to block given the size and cost restrictions of a mobile system. A number of different jammers including frequency modulation radio, television, navigational beacons, and microwave ovens will typically be detected by an omni-directional 2.5 GHz antenna. The low-noise amplifier, therefore, must have a large dynamic range: namely, a low noise figure and low intermodulation distortion. See S. Chen, “Linearity Requirements for Digital Wireless Communi-cation,” IEEE GaAs IC Symp. Dig., Anaheim, Calif., pp. 29-32, October 1997.
To meet these demands, the LNAs often consume the most power in a receiver; tradeoffs are usually required to balance dynamic range versus power consumption.
2. Power Detector
Power detector circuits are many and various, and are not commonly identified as requiring improvement. The low noise amplifier circuit of the present invention will show, however, that it is useful (but not necessary) to detect instantaneous amplifier output power, or (equivalently) voltage (into load), with two orders of magnitude (i.e., ×100) greater sensitivity that existing Schottky diode power detectors. To this end the present invention will be found to encompass a power detection circuit that is particularly characterized in that the power is not detected relative to ground, ergo an un-grounded power detection circuit. When a signal in which power is detected need not be sunk to, nor referenced relative to, ground, then it becomes possible to detect variations in the signal with much greater sensitivity.